1. Field of the Invention
The present invention relates to an organic electroluminescent device comprising an electron shower treated hole injection layer and a method for preparing the same, and more particularly, to an organic electroluminescent device having improved performance and service life characteristics and increased electrical surface resistance of a hole injection layer by performing an electron shower treatment to remove impurities from the hole injection layer, and a method for preparing the organic electroluminescent device.
2. Description of the Related Art
Electroluminescent devices (EL devices) are self emission type display devices based on the principle that electrons and holes are combined to emit light when a current is applied to a fluorescent or phosphorescent organic layer. Because of many advantages such as a thin and lightweight configuration, simple components, a simplified manufacturing process, realization of a high definition and high color purity, low power consumption, and realization of a complete moving picture and full color display, organic EL devices have attracted much attention and have been actively researched.
To improve luminous efficiency and to reduce a driving voltage, the organic EL device generally comprises multiple organic layers including a hole injection layer, an electron transport layer, a hole transport layer, an emitting layer and the like, rather than using a single emitting layer as an organic layer. The multiple organic layers are basically divided into hole-related layers, electron-related layers, and an emitting layer. FIG. 1 is a cross-sectional view of a general organic EL device (e.g., a system employing a small molecular weight emitting layer. Referring to FIG. 1, a stacked structure is illustrated, in which a negative electrode or anode 12 is stacked on a substrate 11, a hole injection layer (HIL) 13 and a hole transport layer (HTL) 14 as hole-related layers are stacked thereon, an electron emitting layer (EML) 15 is stacked thereon, an electron transport layer (ETL) 16 and an electron injection layer (EIL) 17 as electron-related layers are stacked thereon, and a positive electrode or cathode 18 is finally stacked thereon.
In the organic EL device having the stacked structure, the hole injection layer 13 is formed for purposes of reducing a voltage applied, enhancing an emission efficiency and increasing a service life of the device. The hole injection layer 13 is made of copper phthalocyanine, starburst-type amines, e.g., TCTA, or m-TDATA, or poly(3,4-ethylenedioxythiophene) (PEDOT).
However, when the hole injection materials are used for a hole injection layer without a separate treatment, several problems, including deterioration in performance, reduction in electrical surface resistance, and so on, may be undesirably presented due to surface impurities.